Hydraulic pump or motor



Oct. 12, 1965 v. BUSH HYDRAULIC PUMP OR MOTOR 6 Sheets-Sheet 1 Filed001;. 6. 1961 Oct. 12, 1965 V. BUSH HYDRAULIC PUMP 0R MOTOR Filed Oct.6, 1961 6 Sheets-Sheet 2 Oct. 12, 1965 v. BUSH 3,211,107

HYDRAULIC PUMP OR MOTOR Filed 001:. a. 1961 e Sheets-Sheet s Haj.

5/ A 1 r a/we/ Oct. 12, 1965 v. BUSH HYDRAULIC PUMP OR MOTOR 6Sheets-Sheet 4 Filed 001;. 6. 1961 Oct. 12, 1965 v. BUSH 3,211,107

HYDRAULIC PUMP R MOTOR I Filed Oct. 6. 1961 e Sheets-Sheet Mwew 7a,?

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Oct. 12, 1965 v. BUSH 3,211,107

' HYDRAULIC PUMP OR MOTOR Filed Oct. 6. 1961 6 Sheets-Sheet 6 Y Z176. 7g

United States Patent Office 3,211,107 Patented Oct. 12, 1965 3,211,107HYDRAULIC PUMP R MOTOR Vannevar Bush, Jaffrey, N.H., assignor toStewart- Warner Corporation, Chicago, Ill., a corporation of VirginiaFiled (let. 6, 1961, Ser. No. 143,476 Claims. (Cl. 103-174) Thisinvention relates to high pressure hydraulic units, and moreparticularly to hydraulic pump or motor units of the radial piston typehaving one or more variable volume chambers.

One device of this general type includes a housing, a rotatableeccentric, and two mating members movable relative to one .another todefine each variable volume chamber. The first member reciprocatestransversely of the housing while the second member moves on theeccentric in a circular path relative to the housing without rotatingabout its own axis. Relative reciprocation of the members varies thevolume of the chamber and causes a torque about the eccentric mountingto convert between mechanical energy and fluid pressure energy. Inletand outlet means alternately respond to movement of the members forcommunicating a working fluid to and from each chamber.

A major limitation of existing hydraulic units is the presence ofsurfaces which slide upon one another while being pressed together withforces per unit area that can be enormously greater than the fluidpressure. The sliding surfaces must be separated from each other by alubricating film of fluid regardless of the magnitude of the forcespressing the surfaces together. If the supporting film is destroyed,metal-to-metal contact will occur and the life of the unit wil begreatly reduced. The use of a high-viscosity lubricating fluid, whichcannot be readily squeezed out from between the surfaces, isimpracticable because there would be excessive losses due to fluidfriction. Thus, for maximum success, the lubricating film must have aload carrying capacity which increases proportionally to the biasingforces, or the pressure of the working fluid.

A second major limitation of existing hydraulic units is the presence ofcouples, or cocking moments, between mating members such as between thepiston and cylinder and/or between either the piston or cylinder and itsadjacent reaction member. These couples are caused by the manner inwhich reaction torque is transmitted to the machine. The parts arearranged so that the fluid pressure exerts an axial force on the pistonmoving in the cylinder. The force is absorbed by the reaction membersacting on a moment arm to produce a torque about the center of themachine. The reaction torque must be transmitted from one opposingreaction member of the machine through the piston .and cylinder to theother opposing reaction member. Because of the arrangement of parts,there is a couple, or cocking moment, set up which causes the parts tobe tilted with respect to each other. The moment arm of a particularcouple may be very small, resulting in the application of extremelylarge forces. Moreover, due to the tilting, these large forces areapplied over a very small area approaching line contact instead of areacontact. These large forces and small or negligible areas result inenormously large forces per unit area, or pressures, which cannot besupported by an oil film. Metal-to-metal contact will then occur. Thus,it is desirable in a dependable hydraulic machine to eliminate all suchcouples.

Another limitation to full success of any hydraulic unit is leakage ofthe working fluid past the mating parts from the high pressure region orchamber to the low pressure region. Leakage is an importantconsideration since the amount of leakage is proportional to the fluidpressure. When the fluid pressure is low the volume of fluid leaked isgenerally small compared to the active volume of the high pressureregion. But, as the pressure is increased, the fractional part of theworking fluid that leaks rises, and at very high pressures it can becomeintolerable. Consequently, a high pressure hydraulic unit must have highresistance leakage paths past the mating parts between the high and lowpressure regions.

Another limitation and potential problem of high pressure hydraulicunits is porting the working fluid to and from each chamber. Generally,the chamber wall has a port that is covered and uncovered by a movablemember supported on a lubricating film adjacent the wall. As the port isopened, high and low pressure regions are connected resulting in fluidflow through the port and possible displacement of the member intodirect engagement with the wall. To minimize this condition it isdesirable to port the chamber symmetrically of the member to equalizethe high and low pressure regions on opposite sides of the member.

Cavitation of the working fluid within the fluid ports or passages isanother problem relating to porting,-particularly Where the fluid isunder low pressure, as is the intake fluid of a pump. In conventionalhigh pressure hydraulic units of the radial piston type, the workingfluid is communicated to and from the unit in relatively small passagessurrounding the shaft. The shaft, or a coupled extension thereofrotating with the shaft, connects the passages through the fluid portsto the working chamber. All the structure defining the ports andpassages is generally between the axis of the shaft and the workingchambers. This necessarily results in a design wherein the passages arerelatively small, and the ports are quite limited in dimensions. Sinceat high operating speeds there is insuflicient time to accelerate thelow pressure fluid through the small ports and passages without causingcavitation it has been necessary to pressurize the intake fluid of apump.

High pressure piston-type hydraulic units commonly operate at somespecific unchangeable volumetric displacement per cycle. This is adefinite drawback, since frequently it is desirable to vary thedisplacement per cycle for various power requirements, or for variouscyclic frequencies. However, the variable displacement high pressurehydraulic units available in the past generally have been quitecomplicated and lacked dependability for long periods of industrialapplications.

Accordingly, an object of this invention is to provide a high pressurehydraulic pump or motor unit having a combinationof design features thateliminates all couples, or cocking moments, between the adjacent partscaused by the working fluid pressure, and that yields fluid filmscapable of supporting separated from each other the mating surfaces ofthe adjacent parts, regardless of the magnitude of the working pressure.

Another object of this invention is to provide a high pressure hydraulicpump or motor in which leakage of the working fluid between the high andlow pressure regions is minimized.

Another object is to provide a hydraulic unit in which each workingchamber is ported symmetrically to eliminate side thrust of its portcontrolling member.

Another object is to provide a high speed hydraulic pump in which thelow pressure fluid can be ported without cavitation.

Another object is to provide a high pressure hydraulic unit in which thevolumetric displacement per cycle can be adjusted.

Another object is to provide a hydraulic unit that is easily fabricatedwhile yet being dependable in operation.

The particular embodiments of this invention, both as to their structureand mode of operation, will be better understood by reference to thefollowing specification including the drawings forming a part thereofwherein:

FIG. 1 is an elevational view of an embodiment of the hydraulic unitforming a part of this invention;

FIG. 2 is a section view taken on line 22 of FIG. 1;

FIG. 3 is an elevational view, partly in longitudinal section, as seenfrom line 33 of FIG. 2;

FIG. 4 is a perspective view of a cylinder member used in the hydraulicunit;

FIG. 5 is a perspective view of a piston member used in the hydraulicunit;

FIG. 6 is a perspective view of a guide block used in the hydraulicunit;

FIG. 7 is an elevational view of a manifold used in the hydraulic unit;

FIG. 8 is an elevational view as seen from the rear of FIG. 7;

FIG. 9 is an elevational view, partly in section, of a second embodimentof the hydraulic unit forming a part of the invention;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 9;

FIG. 11 is an elevational view, partly in section, of a third embodimentof the hydraulic unit forming a part of this invention;

FIG. 12 is an enlarged view as seen from line 12-12 of FIG. 11;

FIG. 13 is an enlarged view as seen from line 1313 of FIG. 11;

FIG. 14 is an elevational view of a slotted separating port plate usedin a fourth embodiment of this invention; and

FIG. 15 is a sectional view taken on line 15--15 of FIG. 14.

In general, a hydraulic unit utilizing the teachings of this inventionincludes a stationary housing centrally supporting a rotatable shafthaving an eccentric thereon. The housing has concave pockets orchannels, extending transversely of the shaft, which are open toward theeccentric. A cylinder member is matably received in each pocket anddefines a central cylinder open towards the eccentric. A cruciformpiston is rotatably mounted on the eccentric and has radial arms each ofwhich is matably received in one of the cylinders. Upon rotation of theshaft each piston arm reciprocates within its cylinder to define avariable volume chamber, while each cylinder member simultaneouslyreciprocates within its pocket. Each variable volume chamber moves withits defining piston arm and cylinder member so that it is alwaysdisposed symmetrically thereof to eliminate reaction couplestherebetween. A restricted passage intercommunicates the fluid chamberand the interface of the moving and reaction members to establish apressurized supporting fluid film therebetween. The housing hasperipherally located inlet and outlet ports associated with each fluidchamber that separately communicate with the chamber in certain operatepositions of the mating members. The mating members all mate onrelatively large surfaces supported spaced from each other on a film offluid pressurized from the working fluid.

Referring now to the drawings, and particularly to FIGS. 1, 2 and 3, apreferred embodiment includes a housing 10 having spaced port plates 48(FIG. 2) presenting mutually facing substantially parallel surfaces 14that sandwich four spaced shoe members 50 (FIG. 3). Each shoe member 50has an inwardly facing substantially straight surface 16 thereonextending between surfaces 14 of port plates 48. The opposite surfaces16 preferably are parallel to each other and disposed at angles 90 fromthe adjacent surfaces 16. The spaced surfaces 14 of port plates 48 andthe surfaces 16 of shoe members 50 define a generally enclosedrectangular cavity 17 within the housing 10. The cavity 17 may bedescribed as comprising four channels or pockets 12 defined by theconfronting surfaces 14 and each interconnecting surface 16 on the shoemembers 50.

Each pocket 12 matably receives a cylinder member 18, the cylindermember being slidable along a path generally parallel to theinterconnecting surface 16. Each cylinder member 18 (FIG. 4) isgenerally U-shaped, with spaced leg portions 20 defining mutually facingstraight parallel surfaces 22. The surfaces 22, along with the spacedsurfaces 14 of the pocket 12, define a recess or cylinder 19 openinwardly of housing 10.

A single cruciform piston member 24 (FIGS. 3 and 5) is disposedcentrally of the cavity 17 and has four rigid arms 26 each matablyreceived in respective cylinder 19. The piston 24 is mounted centrallyon eccentric portion 28 of a shaft 30 rotatably supported by the housing10. As shaft 30 rotates piston 24 moves in a circular path about theaxis of the shaft without rotation about its own axis. The arms 26 ofpiston 24 mate with cylinder members 18 to move the cylinder memberrelative to the housing 10. Each piston arm 26 thereby reciprocateswithin its mating cylinder member 18 while simultaneously reciprocatingthe cylinder member along the respective surface 16. Since the oppositesurfaces 16 are parallel to each other, the opposite cylinder members 18move in the same direction at the same time. Each cylinder member 18 andits mating piston arm 26 defines a variable volume chamber 32.

The port plates 48 have two aligned inlet ports 34 and two alignedoutlet ports 36 associated with each chamber 32 and terminating atspaced surfaces 14. The edges of inlet ports 34 and outlet ports 36adjacent chamber 32 are preferably parallel to the confronting surfaces22 of cylinder member 18 and spaced apart a distance slightly greaterthan the distance between the surfaces 22. This slight overlap reducesdirect port-to-port leakage. The ports of each chamber 32 are positionedsymmetrically of the top dead center position so that both the inlet andoutlet ports are closed when the piston arm and cylinder member are inthe top dead center position. The length of the adjacent edges of theports are preferably as long as the stroke of piston arm 26.

As the shaft 30 rotates each cylinder member 18 reciprocates along theintermediate pocket surface 16, first to one side of its top dead centerposition, and then to the other side. The inlet ports 34 and outletports 36 are respectively uncovered or opened during each alternatehalf-revolution of shaft 30 by the lateral harmonic displacement of thecylinder member 18. The communicating openings between the respectiveports and each variable volume chamber 32 define generally rectangularslots extending the length of the chamber 32. At all positions of eachcylinder member 18 other than its top dead center positions and thesmall lateral displacement on both sides thereof corresponding to portoverlap, either the inlet ports 34 or the outlet ports 36 are at leastpartially open.

The aligned inlet ports 34 (FIG. 3) are all located clockwise of the topdead center positions, while the aligned outlet ports 36 are all locatedcounterclockwise of the top dead center positions. Consequently, theopposite chambers 32 are always out of phase with each other so that,while top chamber 32 (FIG. 3) is on the intake, the bottom chamber 180away is on the exhaust. Similarly the side chambers 32 are in oppositephases with respect to each other while being out of phase from the topand bottom chambers.

Manifolds 40 (FIGS. 2, 7 and 8) communicate with hydraulic fluid sources(not shown) to supply the ports and chambers with a hydraulic fluid.Hydrauli fluid thus is admitted to each chamber 32 on the inward strokeof piston arm 26 toward shaft 30 and discharged from each chamber on theoutward stroke of the piston arm sure multiplied by the piston area.

away from the shaft. This operation is the same when the unit is used asa pump or as a motor.

The pressure of the fluid in each of the chambers 32 causes a force tobe exerted on the piston arm 26 and cylinder member 18. This force isexerted in a direction parallel to the longitudinal axis of piston arm26 and is equal to the product of the fluid pressure and the area of thepiston. Reaction to this force is absorbed by the eccentric 28 and shoemember 50. This reaction force acting on the effective moment arm of theeccentric 28 about the shaft 30 converts between pressure energy of thefluid and mechanical energy of the shaft.

Each fluid chamber 32 is always located symmetrically of a line disposedparallel to the direction of bias extending through the geometriccenters of the reaction surfaces of the fluid biased members 18 and 24mated with its respective reactive members 50 and 28. The entirereaction caused by the fluid in chamber 32 can be represented as beingtransmitted through these reaction centers. Since the reaction centersare also the geometric centers, the fluid biased members are uniformlybiased against the reaction members 28 and 50. Since there are nocouples caused by the chamber fluid pressure between each fluid biasedmember and its reaction member, there will be no couples between thefluid biased members 18 and 24 themselves. Thus none of the adjacentmating surfaces will be tilted relative to one another by the fluidpressures to affect line contact or to squeeze asymmetrically alubricating fluid film from between the adjacent members.

Two members having mated adjacent surfaces biased together by a forceapplied to the members can be supported separated from each other by alubricating fluid supplied continuously between the mated surfacesintermediate the edges thereof. Flow of the fluid to the edges of themated surfaces establishes a lubricating fluid film between thesurfaces. The roughness characteristics of the mated surfaces determinethe minimum thickness of the fluid film required to prevent directmetal-to-metal contact. The flow characteristics of the lubricatingfluid determine the fluid flow and pressures required to maintain thefluid filmat the minimum thickness.

The film pressure varies from a maximum intermediate the mated surfacesto a minimum at the edges thereof. The leakage of the film past theedges of the mated surfaces varies proportional to the supplied fluidpressure and to the cube of the film thickness. The load supportingcapacity of the film varies proportional to the supplied fluid pressureand to the film area. At balanced conditions, the integratedmathematical product of the film pressure acting on the mating areabetween the members will equal the biasing force to maintain the membersspaced from each other by the thickness of the film.

Since the fluid biasing force on members 18 and 24 against the reactionmember 28 and 50 is proportional to the chamber pressure, it isdesirable that a proportionately high pressure supply the lubricatingfilm at the reaction area between the adjacent members. Passages 42(FIGS. 2 and 3) of restricted cross-section in each of the fluid biasedmembers 18 and 24 extend from the chamber 32 to the interface of theadjacent reaction members 28 and 50. A limited quantity of hydraulicfluid under a proportionately high pressure as that in chamber 32continuously flows from chamber 32 through each passage 42 to thereaction area between the members.

This continuously flowing fluid under pressures proportional to thebiasing force establishes the pressurized lubricating film between theadjacent members.

In order to support the load without metal-to-metal contact, the averagepressure in the lubricating film multiplied by the film area must equalthe chamber pres- The pressure in the chamber 32 is the sum of thepressure drops across the restriction 42 and across the fihn. If thefilm thickness should increase, the film resistance will decrease, thusincreasing the fluid flow. The pressure drop across the restriction willthus increase to reduce the average film pressure. If the film thicknessshould decrease, the opposite will occur, i.e., the flow will decrease,the pressure drop across the restriction will decrease to increase theaverage film pressure. There is only one film thickness at which theaverage film pressure multiplied by the film area will equal the chamberpressure multiplied by the piston area. The film thickness will varyuntil this correct thickness is reached and balance is attained. If thefilm thickness should vary, for any reason, a net force will be exertedwhich will restore the film thickness to the correct value.

In design, it has been established that the restriction should be chosenso that the balance occurs at a film thickness on the order of 0.0005inch. This is a much thicker film than might be needed fromconsiderations of surface roughness because with properly finishedsurfaces the roughness will be approximately 0.000005 inch. Thinnerfilms are not desirable because the force required to shear an oil filmvaries inversely with the film thickness and thus the friction lossesincrease substantially as the film thickness is reduced.

For a positive balance and thus a stable support of loads, it has beenfound that the pressure drop across the restriction 42 should beone-third to one-half of the chamber pressure. The reaction areas arethen chosen to produce the desired film thickness. When the dimensionshave been chosen so that stable operation occurs, the film thicknesswill not change appreciably with chamber pressure. When the chamberpressure is increased, the pressure drop across the restriction and theaverage film pressure both will increase, since the sum of these willalways equal the chamber pressure. But the film thickness will remainnearly constant. This observed fact is extremely important because itpermits operation at very high working pressures without squeezing outthe oil film, thus avoiding metal-to-metal contact. Moreover, a stableoil film limits the high frictional losses which would otherwise occurwith very thin films.

With the design just described oil is supplied to the film only asneeded, thus limiting leakage and the resulting energy losses.

Metal-to-metal contact is avoided only when two conditions are met: (1)there is a stable film capable of supporting the load under alloperating conditions, and (2) the load is applied symmetrically withrespect to the film areas. Condition (1) is achieved as previouslydescribed. Condition (2) will require further explanation.

Referring to FIGURE 3, it will be noted that the useful force exerted bythe fluid in the chamber 32 can act only along a line parallel to thelongitudinal axis of the piston arm 26. This axis passes through thecenter of the eccentric 23 and symmetrically of the base of cylindermember 18, mat-able with shoe member 50. The force acting be tween theeccentric 28 and the shoe member 50 exerts a turning moment about thecenter of shaft 30 that is equal to the force multiplied by theeccentricity normal to the line of application of the force. As theeccentric 28 revolves, a point on the piston 26 moves in a circle whilethe cylinder member 18 oscillates along shoe member 50. The importantpoint is that the torque is always transmitted to the machine by meansof the centrally applied force between the moving eccentric 28 and thestationary sohe member 50 on a moment arm about shaft 30. There are nocouples, or cocking moments, exerted between the members which tend tocock the piston in the cylinder or which tend to tilt the cylindermember 18 with respect to the shoe member 50. In existing hydraulicunits these couples or cocking moments are present and often are verylarge in magnitude. Indeed, in many designs it is the only means oftransmitting torque to the frame of the machine and hence is equal tothe shaft torque. These couples and the resulting tilting moments resultin forces being applied which are asymmetrical with respect "Z to thefluid film separating the members. Such asymmetrical application offorce inevitably destroys the balance previously described and resultsin line contact between the metal surfaces.

Although the description and discussion have referred mainly to thefluid film between cylinder member 18 and shoe member 50, the sameprinciples apply to the fluid film between the bore of the piston 24 andthe eccentric It is thus seen that the combination of balanced oil filmsand the elimination of cocking moments yields a major advance in thedesign of hydraulic equipment.

Considering the construction of the unit more in detail, and referringspecifically to FIGS. 2 and 3, housing includes spaced bearing plates 46having inner sides which sandwich the outer sides of the above-mentionedspaced port plates 48. The inner sides of port plates 48 form thesubstantially flat parallel surfaces 14 of pockets 12. The port plates48 are maintained separated by the previously mentioned four shoemembers 50 and by four guide blocks 52 (FIG. 6). The guide blocks 52each have spaced guide surfaces 56 which face and are spaced from twoadjacent shoe member bearing surfaces 16. Bolts 58 and dowel pins 60extend through aligned openings in the bearing plates 46, port plates48, shoe members 50 and guide blocks 52 to secure them together rigidly.

Hubs 64 (FIG. 2) of bearing plates 46, land the port plates 48 havegenerally aligned central openings 66 extending completely through thehousing 10. The peripheries of openings 66 in bearing plates 46 snuglyreceive the outer races of bearing units 68. The shaft extends throughthe aligned openings 66 in the bearing plates and port plates andengages the inner races of bearing units 68. Bearing units 68 preferablyare self aligning double guide roller bearings which adequately supportthe shaft 30 against both longitudinal and lateral forces. The eccentric28 is a generally cylindrical section integral with or keyed to shaft 30intermediate the inner races of bearing units 68. The eccentric 28 isdisposed to rotate within the central openings 66 of the port plates 48.

End plates 70 engage the hubs 64 of bearing plates 46 and have O-ringgaskets 71 disposed to ensure a sealed fit therebetween. Bolts (notshown) extend through openings in the end plates 70 into threaded tapsin the hubs 64 to secure the two together. Each end plate 70 has acentral aperture 72 through which the shaft 30 extends. Annular spacerelements 74 are tightly received on shaft 30 over interposed O-ringgaskets 75 and are rotatable as a unit with the shaft. Each spacer 74 isreceived in the end plate aperture 72 and rotatable therein in sealingrelationship with O-ring gasket 77. A threaded bore 76 through each endplate 70 to the interior or sump space of the unit provides forconnection to a hydraulic line (not shown).

Counter-weights 78, keyed to shaft 30 adjacent end plates 70, equalizethe dynamic unbalance caused by the rotating piston 24 and reciprocatingcylinder members 18. Since all of the moving parts follow predeterminedpaths in parallel planes, dynamic balancing can be achieved by the twocounter-weights 78, as is well known in the art. Cup-shaped covers 80each having a central base opening 79 and a peripheral slot 81 covercounter-weights 78 and end plates 70 and are secured to the end platesby appropriate means (not shown). Nuts 82 threaded onto the threadedportions of shaft 30 tightly engage interposed lock washers 83 andcounter-weights 78.

Thus the eccentric 28, inner races of the bearing units 68, the spacers74, and counter-weights 78 rotate as a unit with the shaft 30. It is tobe understood that there is suflicient axial clearance between piston 24and the hearing units 68 to permit relative rotation between the memberswithout binding or excessive wear. Keyed portions 84 of shaft 30 projectoutwardly of end covers 80 for connection to a mechanical device such asa driving motor (not shown) or to a driven unit (not shown) dependingwhether the unit is used as a pump or motor.

Annular oil jacket 86 surrounds the unit 10 at its midportion and issealed thereto by a pair of O-ring gaskets 87 disposed in annularnotches in the bearing plates 46. Port plates 48 preferably haveenlarged recesses 89 (FIG. 2) adjacent the ports remote from eachchamber 32 which reduce the hydraulic flow resistance through each port.Passages 91 in bearing plates 46 intercommunicate recesses 89 in theport plates 48 with a plurality of uniformly spaced counterboredopenings 93. The interior or sump space of the unit is completely sealedby the various O-ring gaskets. The only paths by which hydraulic fluidcan enter or leave the unit is through the threaded bores 76 in the endplates 70 and the openings 93 in bearing plates 46.

Manifolds 40 connect each chamber communicating openings 93 with theappropriate intake or exhaust hydraulic source (not shown). Eachmanifold 40 has an inner tube 88 and an outer tube (FIGS. 2 and 7)having communicating pipes 92 projecting from the tubes towards thehousing. A stepped flange 94 on the free end of pipe 92 is secured tobearing plate 46 against interposed Oring gasket 95 and into thecounterbored opening 93. The manifolds 48 are identical so that adjacentpipes 92 are alternately connected to the inner and outer tubes 88 and90 to correspond to the alternate positioning of the inlet ports 34 andoutlet ports 36 about the unit. Consequently, as viewed in FIG. 2 theouter tube 90 on the left manifold 40 and the inner tube 88 on the rightmanifold 40 are associated with the intake fluid, while inner tube 88 onthe left manifold and the outer tube 90 on the right manifold areassociated with the exhaust fluid. Passages 96 (FIGS. 1 and 7) extendfrom the intake and exhaust tubes in each manifold and secure Tconnections 1% between opposed flanges 98. The Ts 100 each have athreaded bore 101 which receive a tube (not shown) respectivelyconnected to the intake and exhaust sources of fluid (not shown).

Consequently, any fluid directed to the intake T 100 is delivered toopposite sides of chamber 32 equally. The fluid is similarly exhaustedfrom opposite sides of chamber 32 through two manifolds having equalfluid pressures. This symmetric porting of each chamber equalizes thehigh or low pressure regions on opposite sides of the cylinder member 18and piston arm 26 to eliminate biasing fluid forces tending to moveeither member towards one port plate 48 or the other.

It can be noted in FIGS. 2 and 3 that the fluid ports 34 and 36 andmanifolds 40 are located on the periphery of the unit adjacent thechambers 32. This arrangement permits the cross-section of both theports and manifolds to be large and of adequate sizecompared to themaximum volume of each chamber 32. Consequently, for each working strokeof any piston arm 26, the fluid in the manifold is displaced only ashort distance. Even when the unit is operating at a high speed and eachworking stroke takes only a fraction of a second, the fluid in manifold40 only needs to be accelerated slightly to keep up with the fullvolumetric displacement. This is particularly true since each chamber 32is supplied by two manifolds through two ports. This porting arrangementreduces cavitation to such an extent that high speed pumping operationsare generally possible without the necessity of having a pressurizedintake.

FIG. 4 shows one of the cylinder members 18 in perspective. Eachcylinder member 18 includes a generally U-shaped body portion havingopposed flat parallel surfaces 102 closely matable when assembled in thepocket 12 with the surfaces 14 of port plates 48. The base portion has astraight surface 104 partly defined by protruding toes 106 having flatsurfaces 108 therein oppositely facing and extending parallel to surface164. The surface 104 mates with and reciprocates along bearing surface16 of the shoe member 50 while the toes 9 106 extend between the guidesurfaces 56 of the guide blocks 52 and the bearing surface 16. Thedistance between guide surfaces 56 and bearing surface 16 is slightlygreater than the distance between the surfaces 104 and 108 to providefor free cylinder member movement therebetween. Surfaces 56 and 108 areengageable only when the unit has stopped and gravity or residual fluidpressure between the surfaces 104 and 16 biases cylinder member 18 fromsurface 16.

Leg portions .20 define the mutually facing straight surfaces or'faces22, previously mentioned, which extend parallel to each other andperpendicular to straight surface 104 symmetrically of its ends. Basesurface 110 extends between surfaces 22 and surfaces 102. A shallowgroove or slot 116 extends along the intermediate portion of bearingsurface 104 spaced from the edges thereof and is interconnected withbase surface 110 by aperture 118. An insert 120 secured within theaperture 118 has a through-bore of very small cross-section, generallyonly a few thousandths of an inch in diameter, which defines one of theabove-mentioned restricted passages 42.

Generally C-shaped braces 122 fit over the free ends of legs 20 andengage flat surfaces 112 and ribs 114. Bolts 124 extend throughinterposed lock washers 126 and the apertures 125 in braces 122 intothreaded taps 123 in surface 112. The braces 122 constrain the free endsof the legs 20 from cantilever type deflection when hydraulic pressureis generated in chamber 32. Surfaces 22, which define two sides ofchamber 32, are located symmetrically from the ends of the cylindermember along the bearing surface 104. Thus fluid pressure in chamber 32will uniformly bias the cylinder member 18 against shoe member 58,causing no couples tending to establish line contact between theadjacent surfaces 16 and 104.

FIG. shows a preferred form of the cruciform piston 24, which includeshub 128 having central cylindrical through bore 130. Arms 26 projectfrom hub 128 radially of the bore 130 and are spaced 90 apart. Each armis of uniform rectangular cross-section defined by flat parallelsurfaces 132- disposed perpendicular to the axis of said bore, straightparallel surfaces 134 disposed ferential groove or slot 138 in theperiphery of throughbore 130 extends over an arc of approximately 70equidistantly of the center of each piston arm 26. Opening 140 in eachpiston arm 26 extending between the slot 138 and surface 136, receivesan insert 142 therein having a through passage of very smallcross-section which defines one of the previously mentioned restrictedpassages 42.

During operation of the unit, hydraulic fluid enters each chamber 32through inlet ports 34 and is discharged from the chamber through outletports 36. Regardless of whether the unit is used as a pump or motor, thefluid in each chamber 32 is under high pressure at some time during thecycle. The pressurized fluid acts on surfaces 110 and 136 of thecylinder member and piston, respectively, to bias them apart in thedirection of piston arm 26 and cylinder 19. Since each chamber 32 issymmetrically disposed with respect to the reaction areas of itsdefining moving members 18 and 24, the fluid biasing force produces nocouples between the members. Reaction of this biasing force is absorbedby shoe member 50 and by eccentric 28.

Each restricted passage 42 communicates limited quantities of highpressure fluid from the chamber 32 to slots 116 and 138 in theinter-faces between the fluid biased members 18 and 24 and the reactionmembers 28 and 50. The hydraulic film varies in pressure somewhatlinearly from its high at the slot to its low at the edges of the sur-18 face. Even though piston 24 is biased toward eccentric 28, and thecylinder member 18 toward the shoe member 50, by the continuinglychanging resultant force from the changing fluid pressures withinchamber 32, a supporting fluid film is maintained between the matingadjacent surfaces. The reasons for this are two-fold, since: (1) eachchamber 32 communicates directly with the above-mentioned reaction areasto establish a proportionately high pressure supporting film, and (2)there are no couples between any of the mating surfaces caused by thefluid pressure to reduce area contact to line contact. Consequently atall times the moving fluid biased members 18 and 24- are floated onhydraulic film-s adjacent the respective reaction members 50 and 28.

The fluid forced from chamber 32 past the mating surfaces 102 and 14 isdirected to the sump space. The fluid forced past the shoe member 50 andthe cylinder member 18 is directed in part to the peripheral region 146(FIG. 3) of the unit. The oil in the peripheral region 146 is circulatedin the oil jacket 86 and admitted to the sump space between the guideblocks 52 and cylinder members 18. Slots 148 (FIG. 6) in the guideblocks decrease the flow resistance of the fluid to the sump space. Thefluid collected in the sump space is communicated through bores 76 inend plates 70 to the reservoir of the hydraulic system.

Since each cylinder member 18 and piston arm 26 are matable With thespaced surfaces 14 of the pocket, the flow path from the high pressureof the low pressure region is long and of high resistance. The leakagefrom each chamber 32 thus is minimized. However, any leakage is nottotally wasted as it lubricates the members for friction free movementsrelative to each other.

FIGS. 9 and 10 show a second embodiment similar in part to that alreadydisclosed. Like components will thus be designated with the samereference numerals. The embodiment includes housing 10a having bearingplates 46a sandwiching a plurality of separating port plates 48a, shoemembers 50a and guide blocks 52a. Housing 10a is secured together, andto supporting feet 154 by through bolts 58a. Shaft 38a extends throughaligned openings in the bearing plates 46a and is supported for rotationwith; in bearing units 68a. Three cylindrical eccentric portions 28a arekeyed or otherwise formed adjacent each other on shaft 30a, the end orouter eccentrics being in phase, with respect to the longitudinal axisof the shaft, and 180 out of phase with the intermediate eccentric.

Cylinder members 18a reciprocate in pockets 12a defined by port plates48a and shoe members 50a. Three pistons 24a each having four equallyspaced radial arms 26a are respectively disposed on the eccentricportions 28a, with arms 26a matable with the cylinder members 18a.Rotation of shaft 30a reciprocates the three pistons 24a relative eachmating cylinder member 18a while simultaneously reciprocating thecylinder member along bearing surface 16a. The reciprocating piston arms26a and cylinder members 18a define the variable volume chambers 32a.Thus, each piston 24a and its mating cylinder members 18a, represent astage similar to that of the fiirst embodiment.

Each chamber 32a is symmetrically ported in the manner substantially asthat already disclosed. However, the inlet ports 34a and outlet ports36a communicate respectively with internal radial passages and 162 inport plates 48a. The passages 160 and 162 communicate respectively withspaced longitudinally extending channels 164 and 166 through the portplates 48a and shoe mem bers 50a. Each of the channels 164 and 166extends to an annular inlet 168 or outlet 170 internal manifold in oneor the other of the bearing plates 46a. Threaded bores 174 and 176 inthe bearing plates communicate respectively with the inlet and outletmanifolds 168 and .170 providing ready connection means to the hydraulisources (not shown).

The inlet annular manifold 168 thus communicates 1 1 with eachlongitudinal passage 164 which in turn communicates with the inlet ports34a through the radial passages 160. Similarly, the outlet annularmanifold 170 communicates with each outlet port 36a through longitudinalpassages 166 and radial passages 162.

Each reciprocating cylinder member 18a alternately covers and uncoversthe inlet and outlet ports for communicating the hydraulic source withthe defined chamber 32a. As shown in FIG. 10, upper chambers 32a of theouter stages are on intake, while the lower chambers of the outer stagesare on exhaust. Conversely the upper and lower chambers of theintermediate stage are on exhaust and intake, respectively.

Preferably the piston arm areas of surfaces 136a of the outer stages areequal, with their combined areas being equal to the piston arm areas ofthe inner stage. Since the strokes of each stage are the same, the fluiddelivery and torque of the outer stages are equal to and 180 out ofphase with the inner stage. Also, since the opposite piston arms of theinner and outer stages are simultaneously operating on the same phase ofthe cycle (either intake or exhaust), the opposed biasing forces of thestages do not appear as loads on the bearings 68a, but substantiallycancel each other. Similarly the unit is balanced dynamically since themass of the outer stages counteracts the mass of the inner stage.

FIGS. 11, 12 and 13 disclose a third embodiment which is particularlyadaptable as a variable displacement hydraulic unit. A pair of frames180 and 182 secured together by bolts 184 clamp two adjacent housings186 and 188 snugly against one another. Shaft 30b is rotatably mountedon hearing units 68b and has two adjacent eccentric portions 281) inpositional relationship 180 out of phase with respect to each other.Housing 186 is aligned with one eccentric 28b and is fixed rigidly tothe frame 180. Housing 188 is aligned with the other eccentric 28b andis movable about shaft 301) relative to the fixed hous ing 186. Themovable housing 188 is rotated by hand wheel 190 fixed on shaft 191through mating worm gear 192 and annular rack 194 secured respectivelyto shaft 191 and housing 188.

The housings include spaced separating plates 48b and 196, and 198 and200, respectively, which sandwich shoe members 50b and guide blocks 52bto define the inwardly facing C-shaped pockets 12b. Cylinder members 18band arms 26b of piston 24b are matably disposed in the pockets andreciprocate relative to each other to define variable volume chambers32b. The pistons 24b in each housing are actuated by eccentric portions28b on shaft 30b.

To simplify the disclosure of the fundamental operation of the unit eachstage is shown to have only two chambers 32b. It will be understood,however, that the preferred embodiment will include more than twochambers per stage, presumably four equally spaced chambers as shown inthe first two embodiments.

The separating plate 48b of fixed housing 186 has an inlet port 34b andan outlet port 36b associated with each chamber 321?, and is similar tothe port plates previously described. Separating plate 196 of fixedhousing 186 has shallow indentations or blind ports (not shown) alignedwith the inlet ports 34b and outlet ports 36b of plate 48b. The shallowindentations balance in part the low pressure region in the chambercaused by porting of the fluid. The separating plates .198 and 200 ofmoving housing .188 have no inlet and outlet ports therein, but haveopenings and slots to be discussed hereinafter.

The separating plates 196 and 1 98 have adjacent surfaces that aresubstantially identical. The mating surfaces have a series of separatelymatched slots 2 extending circularly about the shaft b at given radiieach through -an angle of approximately 90 as shown in phantom in FIG.13. The matched slots of the plates overlap to form a continuous passagefrom one end of one slot to the opposite end of the other slot through amaxieliminating couples between the members.

mum angle equal to the arc of the two matched slots, minus the overlap,or [approximately 1 Openings .204 extend through each separating plateand communicate with the slots 202 therein. The openings 204 are spacedapart and at a common radius from the center of the plates tocommunicate the variable volume chambers 32b of one stage with like orcorresponding chambers 32b of the other stage. Each chamber 32b of thestationary housing 186 thus has a continuous fluid communicating passagewith the corresponding chamber 32b of the movable housing 188.

As shown in FIG. 13 the two housings are rotated an angle A relative toone another so that the intercommunicated chambers are in other thanphase relationship. When angle A is equal to 0 the stages are in phaseand the corresponding pistons of each stage move in the same directionat the same time relative to its mating cylinder member. Thus, theintercommunicated chambers 32b are on intake or on exhaust at the sametime. Consequently, when inlet port 3412 in fixed housing 186 is openthe fluid is communicated to the intercommunicated chambers 32b in thefixed and movable housings to fill both chambers completely. Thereciprocating cylinder members of the stationary housing 186 control theporting to and from the chambers of both housings.

When the stages are in phase (when angle A is equal to 0) the totalhydraulic flow to and from the unit is additive and is equal to the sumof the intercommunicated chamber volumes. As the housings are rotatedrelative to each other and angle A becomes larger than 0", the stagesare actuated in out-of-phase relationship. The total fluid fiow to andfrom the unit will then be reduced. This is because the volume change ofchambers 32b in fixed housing 186 is partially counteracted by adifferent volume change of its intercommunicated chambers 32b in movinghousing .188 for an incremental rotation of the shaft 30b.

When the two stages are rotated so that angle A is equal to 180, thestages are in opposite phase relationship with respect to each other.The volume changes of the intercommunicated chambers are thensubstantially opposite each other for a given rotation of the shaft3017. Consequently, the total volume to and from the unit is effectivelyreduced to zero. The hydraulic fluid in the unit is surged back andforth between the intercommunicated chambers in the stationary andmovable housings.

Thus, the resultant how to and from the unit can be varied as desiredfrom its maximum displacement (the sum of the two stages) when thestages are in phase to its minimum displacement (approximately zero)when the stages are 180 out of phase.

FIGS. 14 and 15 show a separating plate, corresponding to plate 198 ofFIG. 11, operable for a variable displacement hydraulic unit having fourequally spaced chambers for each stage. The plate has matched slots 205on two different radii and chamber communicating openings 208. Radialpassages 210 between the larger radius slots 206 and openings 208 alignthe openings 208 with the chambers 3212, while yet not interfering withthe separate independent action of each slot. llug 212 closes the outerend of passage 210.

It is thus seen that the teachings of this invention have substantiallyeliminated the defects of prior hydraulic units. The fiuid pressuresgenerated in the unit are transmitted through reaction centers of thevarious chamber defining members symmetrically of the members, thus Thefluid biased members are floated spaced from the reaction members on acontinuous pressurized fluid film. Each fluid chamber is defined bymating members having high resistance flow paths therebetween to minimumleakage. Fluid porting of each chamber is ample to eliminate cavitation.The various hydraulic units disclosed are reliable, while yet notprohibitive by construction cost or complex components.

Various embodiments disclosed herein have been built to operate atspeeds up to 5,000 r.p.-m. and the fluid pressures up to 5,000 psi. Aunit similar to that described in FIG. 1 having 1" square piston armswith a /2" stroke has a total displacement "of 2 cubic inches perrevolution. The flow rate is approximately 45 gallons per minute at 125hydraulic horsepower. The unit weighs but 65 pounds.

A unit as disclosed in FIG. 9 having intermediate stage piston arms /2"by /2" with the outer stage piston arms /2" x A" has approximately 40gallons per minute fluid flow with 120 hydraulic horsepower. The unitweighs approximately 75 pounds.

While various specific embodiments have been shown, it will be obviousto those skilled in the art that many changes can be made withoutdeparting from the spirit of the invention. Thus, while the embodimentsshown included stagm having two or four equally spaced chambers,

many other chamber combinations for each stage are possible. Thus ahydraulic unit having stages with three,

a first member received in the pocket and having a straight bearingsurface matably adjacent the support surface and reciprocable thereon, asecond member matable with the first member and the opposite surfaces ofthe pocket and movable relative thereto to define a variable volumechamber, said second member having a generally smooth bearing surfacefacing oppositely the first member bearing surface, a shaft supportedfor rotation in the housing and having a smooth support surface matablyadjacent and movable relative to the second member bearing surface andmovable toward and away from the housing support surface for moving themembers relative to one another and to the housing, and inlet and outletmeans in the opposite surfaces associated with the chamber for supplyinghydraulic fluid to and from the chamber, each of the first and secondmembers having a through passage of restricted cross-sectional areaextending between its bearing surface and the chamber for establishing apressurized film of hydraulic fluid between the matably adjacentsurfaces to support the mem- 2. A hydraulic pump or motor comprising ahousing including a pocket defined by opposite walls and aninterconnecting wall, a generally U-shaped cylinder member matablyreceived in the pocket and reciprocable therein and having leg portionsdefining a cylinder with the opposite walls of the pocket, a pistonmatably received in the cylinder and adapted to reciprocate therein in adirection transverse to the direction of reciprocation of said cylindermember, and means for reciprocating the piston in the cylinder to definea variable volume chamber while simultaneously reciprocating thecylinder member within the pocket, said opposite walls each having aninlet and an outlet port associated with the chamber positioned to becovered'by the cylinder member at certain operative positions andselectively opened by the cylinder member at other operative positionsto communicate with the chamber.

3. A hydraulic pump or motor unit comprising a housing including threesurfaces, two of which are spaced and parallel, the third of whichextends perpendicularly between the two to define a generally C-shapedpocket, a cylinder member received in the pocket and defined by threesurfaces two of which are spaced and parallel, the third of whichextends perpendicularly between the two and matably with the thirdhousing surface, said cylinder member being reciprocable in the pocketparallel to all of the surfaces, said cylinder member being U-shaped andhaving leg portions defining with the two spaced surfaces of the housinga cylinder of uniform cross-section extending perpendicular to the thirdsurface, a piston having a generally uniform cross-section matablyreceived within the cylinder and reciprocable relative thereto to definea variable volume chamber, means for reciprocating the piston relativeto the cylinder member to vary the chamber volume between maximum andminimum volumes respectively at top dead center positions whilealternately reciprocating the cylinder member across the top dead centerpositions to either side thereof, and aligned inlet and outlet portsdisposed in the two spaced surfaces of the housing adapted to be coveredby the cylinder member at the top dead center positions, andrespectively opened by the cylinder member on opposite sides thereof tocommunicate with the chamber.

4. A hydraulic pump or motor comprising a housing including a pluralityof inwardly facing pockets each defined by opposite walls and aninterconnecting wall, a first member matably received in each pocket andreciprocable therein, a second member having a center through-bore and acorresponding plurality of radially projecting arms each matable withone of the first members and opposite walls to define with said firstmembers and said opposite walls a plurality of chambers, a shaft havingan eccentric matably received within the throughbore, said eccentricbeing operable upon rotation to dis place the second member in acircular path to reciprocate the arms with respect to the first membersand to simultaneously reciprocate the first members within the pockets,the opposite walls of each pocket having aligned inlet ports and alignedoutlet ports separately connectable to the respective chambers andcovered by the respective members at certain operative positions withinthe pocket and selectively opened by the members at other operativepositions to communicate with the chamber.

5. A hydraulic pump or motor comprising a housing including a pluralityof inwardly facing pockets each having mutually facing parallelsurfaces, a U-shaped cylinder member received in each pocket andreciprocable therein along a fixed path and defining with the housingsurfaces a cylinder opened inwardly of uniform cross- .section extendingperpendicular to the path, a piston having a center through-bore and acorresponding plurality of radially projecting arms having uniformcrosssections each matably received in a respective cylinder, a shaftmember having and eccentric matably received within the through-bore andoperable upon rotation to displace the piston member in a circular path,to reciprocate the piston arms with respect to said cylinder members ina direction transverse to the direction of said fixed path to definevariable volume chambers, said eccentric also being operable toreciprocate the cylinder members to the extremes of their respectivepaths, each chamber having a maximum and minimum volume respectively atan operative position of the cylinder member intermediate said extremes,each chamber having associated therewith aligned pairs of inlet andoutlet ports in the opposite surfaces alternately covered and uncoveredby the cylinder member in the positions thereof toward the oppositeextremes of its path.

6. A hydraulic pump or motor unit comprising a housing, a shaftrotatably mounted centrally of the housing and having an eccentricportion thereon, said housing having a plurality of circumferentiallyspaced pockets open toward and symmetrical of the eccentric portion,each of said pockets being defined in part by mutually facing oppositewalls, a generally U-shaped cylinder member matably received in each ofthe pockets, the leg portions of the cylinder members and the oppositesides of the pockets defining cylinders open towards the shaft, eachcylinder member being movable in its pocket along a path extendingtransversely of the shaft, and a piston member rotatably mountedcentrally on the eccentric portion and having radial arms matablyreceived in the cylinders to reciprocate the piston arms within thecylinders to define variable volume chambers while simultaneouslyreciprocating the cylinder members along their respective paths, theopposite walls of each pocket having aligned inlet ports and alignedoutlet ports alternately and separately opened by the cylinder membertherein to communicate with the chamber.

7. A hydraulic pump or motor unit comprising a housing having spacedparallel surfaces interconnected by two pairs of parallel mutuallyfacing bearing surfaces angularly disposed 90 with respect to eachother, said surfaces defining four inwardly facing pockets, a U- shapedcylinder member received in each pocket, the base portion of saidcylinder member having a bearing surface matably adjacent the housingbearing surface and reciprocable thereon, the leg portions of saidcylinder member having mutually facing bearing faces extendingperpendicular to the bearing surface, a rigid cruciform piston memberhaving a central bore and four equally spaced radial arms matablyreceived between the leg portions with each arm having peripheralsurfaces engaging the bearing faces thereof and the spaced pocketsurfaces, said arms being reciprocable relative to said leg portions todefine four variable volume chambers, a shaft supported by the housinghaving an eccentric matably received within the bore and operable uponrotation to displace the piston member in a circular path within thehousing to vary the chamber volumes while simultaneously reciprocatingthe cylinder members, and inlet and outlet port means in the spacedpocket surfaces on opposite sides of the piston member selectivelyopened by the reciprocating cylinder member to communicate with thechambers.

8. A hydraulic pump or motor comprising a housing having spaced parallelflat surfaces interconnected by a plurality of inwardly facing straightbearing surfaces to define inwardly facing pockets, a generally U-shapedcylinder member received in each pocket with its base portion having astraight bearing surface matably adjacent the inwardly facing bearingsurfaces and its leg portions having spaced mutually facing facesextending perpendicular to the bearing surface, a piston disposed in thehousing and having a central through-bore and a corresponding pluralityof radially projecting arms having exterior surfaces matably receivedbetween the leg portions of each member and the pockets to definevariable volume chambers therebetween, and a shaft supported centrallyof the housing and having an eccentric received by and engaging theperiphery of the through-bore and operable upon rotation thereof todisplace the piston member in a circular path, thereby reciprocating thepiston arms relative each member while simultaneously reciprocating themembers in the pockets along paths parallel to the respective bearingsurfaces, said housing having inlet and outlet ports associated witheach pocket closed by the cylinder member therein at certain operativepositions, and separately opened at other operative positions tocommunicate with each of the chambers, said members each having athrough passage of restricted cross-sectional area extending between itsbearing surface and the chamber, each of the piston arms having athrough passage of restricted cross-sectional area extending between theperiphery of the through-bore and the chamber.

9. A hydraulic pump or motor unit comprising a housing, a shaftrotatably secured centrally of the housing and having a plurality ofaxially spaced adjacent eccentric portions each disposed in out-of-phasepositional relationship with its adjacent portion, said housing having aplurality of axially spaced cavities each associated with one of saideccentric portions, each of said cavities comprising a plurality ofpockets opened toward said shaft each being defined in part by mutuallyfacing opposite surfaces, a generally U-shaped cylinder member matablyreceived in each of the pockets so that its leg portions along with theopposite surfaces of the pockets define a cylinder open towards theshaft, each cylinder member being movable in its pocket along a pathextending transversely of the shaft, a piston rotatably mountedcentrally on each eccentric portion and having radial arms projectingrespectively toward the pockets associated with the respective eccentricportion, said arms being matably received in the cylinders andreciprocal therein upon rotation of the shaft to define variable volumechambers, said arms adapted to simultaneously reciprocate the cylindermembers along their respective paths, the opposite surfaces of eachpocket having aligned pairs of inlet and outlet ports alternately openedby the cylinder member therein to communicate with the chamber.

10. A hydraulic pump or motor unit, comprising a housing, a shaftrotatably supported by the housing centrally thereof, a plurality ofbearing surfaces on the housing spaced radially of the shaft, aplurality of first members matable respectively, with each bearingsurface and reciprocable thereon, a second member rotatably mounted onthe shaft and having radially extending arms matable respectively, witheach of the first members, means to move the second member relative toeach of the first members to define a plurality of variable volumechambers spaced radially of the shaft, said housing defining alignedpairs of inlet and outlet ports for each chamber disposed on both sidesof and adjacent the respective chamber, and inlet and outlet manifoldsextending annularly of the shaft adjacent the respective ports fordirecting a hydraulic fluid to and from the unit, said ports andmanifolds being of such size, compared to the working volume of eachchamber, that the fluid acceleration therein is small for all operatingspeeds of the unit.

11. A hydraulic pump or motor unit, comprising a housing, a shaftrotatably supported by the housing centrally thereof, an eccentricsecured to the shaft, a plurality of inwardly facing bearing surfaces onthe housing spaced radially of the eccentric, a plurality of firstmembers matable respectively, with each bearing surface and reciprocablethereon, a second member rotatably mounted on the eccentric and havingradially extending arms projecting respectivey, normal to the bearingsurfaces and matable with each of the first members therein, whereinrotation of the shaft moves the second member relative to each of thefirst members to define a plurality of variable volume chambers spacedradially of the shaft, aligned pairs of inlet and outlet ports for eachchamber defined by the housing on both sides of each chamber anddisposed adjacent the chambers longitudinally of the shaft, and inletand outlet manifolds extending annularly of the shaft adjacent therespective ports on both sides of the chambers for directing a hydraulicfluid to and from the unit, said ports and manifolds being of such size,compared to the working volume of the chambers, that the fluidacceleration therein is small for all operating speeds of the unit.

12. A hydraulic pump or motor unit, comprising a housing having aplurality of inwardly facing pockets each defined by opposing walls andan interconnecting wall, a plurality of first members each matablyreceived in one of the pockets and reciprocable therein along theinterconnecting wall, a second member having a center throughbore and acorresponding plurality of radial projections extending normal to therespective interconnecting wall, each radial projection being matablewith one of the first members and the opposing walls to define aplurality of fl d c ambers each disposed symmetrically of the firstmember with respect to the portion thereof mated with theinterconnecting wall, a shaft rotatable in the housing, an eccentric onthe shaft matably received in the throughbore and operable to displacethe second member in a generally circular path and to reciprocate thefirst members within the pockets thereby varying the volume of thechambers, each of said opposing walls of each pocket having alignedinlet and outlet ports spaced apart in the direction of movement of thefirst member and adjacent the chamber adapted to communicate separatelytherewith at certain operative positions of the first and secondmembers, and means including restricted through-passages in the firstand second members extending between the chambers and the interfaces ofthe members, respectively, adjacent the interconnecting walls andeccentric.

13. A hydraulic pump or motor unit, comprising in combination, fluidbiased means including a pair of mating members reciprocable in a firstdirection relative to one another to define a variable volume fluidchamber, reaction means opposing the fluid biased means and including astraight bearing surface extending in a second direction normal to thefirst direction and a cylindrical eccentric spaced therefrom in thefirst direction rotatable about an axis normal to the first and seconddirections, one of the mating members being reciprocable on the bearingsurface in said second direction and the other of the members beingtranslatable on the eccentric in a circular path about said axis, eachof said members having a passage of restricted cross-sectioncommunicating with the fluid chamber and terminating at the interfaceadjacent the respective reaction means operable to establish by leakagea fluid film and to cause a pressure drop comparable to the pressuredrop across the fluid film itself under normal film clearance and flowconditions, the fluid biased means mating with the reaction means in allrelative positions thereof symmetrically of lines extending in the firstdirection through the center of the fluid chamber, means to rotate theeccentric about the axis for converting between fluid and mechanicalenergies, and means to port the fluid chambers.

14. A hydraulic pump or motor unit, comprising in combination, aplurality of fluid biased means each including a common member and anindependent member mating therewith and reciprocable in a firstdirection relative thereto to define a variable volume chamber, saidfirst directions all extending normal to a common axis, reactive meansopposing each fluid biased means and including a cylindrical eccentricrotatable about said axis and a corresponding plurality of straightbearing surfaces spaced therefrom in the respective first direction andextending in a second direction generally normal to the first direction,the independent mating member of each fluid biased means beingreciprocable on the bearing surface of the corresponding reaction meansin said second direction and the common mating member being translatableon the eccentric in a circular path about said axis, each of the matingmembers having a passage of restricted cross-section communicating withits defined fluid chamber and terminating at the interface adjacent therespective reaction means operable to establish by leakage a fluid filmat the interface, said passage causing a pressure drop under normal filmclearance and flow conditions of approximately /s to /2 the pressure inthe fluid chamber, the fluid biased means mating with its respectivereaction means in all relative positions thereof symmetrically of linesextending in the corresponding first direction through the center of itsdefined fluid chamber, means to rotate the eccentric about the axis forconverting between fluid and mechanical energies, and means to port thefluid chambers.

15. A hydraulic pump or motor unit, comprising in combination, a pair ofmating members constituting respectively, a piston member and a cylindermember, said mating members being reciprocable relative to one anotheralong a first path parallel to the longitudinal center axis of thepiston to define a variable volume fluid chamber of a givencross-section normal to said first path, each of said mating membershaving a reaction area larger than said chamber cross-section andextending transversely to and symmetrically of said center axis, a pairof opposing members disposed outwardly of said mating memberscontrolling the relative movement thereof, said opposing members eachhaving an opposing reaction area complementary to and adjacent thereaction area of the adjacent mating member, one of said opposingmembers having a longitudinal center axis intersecting saidfirstmentioned axis and extending generally parallel to said matingmember reaction areas, means to move the secondmentioned axis and theother of the opposing members relative to one another in a generallycircular path about an axis parallel to said second-mentioned axis tovary the shortest distance between said opposing reaction areas whilesimultaneously displacing the axis defining said shortest distance in asecond path transverse to said first path, and means to supply a fluidto said chamber, thereby biasing the mating members apart along saidfirst path and against said opposing members with a force equal to achamber fluid pressure acting on said chamber crosssection, each of saidmating members having a through restricted passage between the chamberand the interface of its reaction area, said restricted passage beingoperable to communicate a limited quantity of fluid at a second pressureless than the chamber pressure to between the adjacent reaction areas tosupport the areas spaced from each other on a fluid film having anaverage pressure less than the second pressure, the mathematical productof the average film pressure acting on the respective adjacent reactionareas always seeking to equal the mathematical product of the chamberpressure acting on said chamber cross-section and the pressure dropacross the restricted passage being /2, to /2 that of the fluid pressurein the chamber and being comparable to the pressure drop across thefluid film itself.

References Cited by the Examiner UNITED STATES PATENTS 360,057 3/87Smith 121-52 388,522 8/88 Beauchemin 103-161 X 580,838 4/97 Almond103-161 X 1,082,224 12/13 Crayssac 103-161 X 1,455,753 5/23 Mayer 121-521,630,953 5/27 Levine 121-52 1,757,483 5/30 Hele-Shaw et al 103-1612,013,862 9/35 Schulz et al. 103-163 X 2,130,037 9/38 Skarlund 103-1632,347,663 5/44 Carnahan 103-174 X 2,561,519 7/51 Leech 103-37 2,573,47210/51 Martin 103-174 X 2,675,763 4/54 Muller 103-161 2,679,210 5/54Muller 103-161 2,833,225 5/58 Sherman 103-161 2,851,952 9/58 Lane 103-372,968,287 1/61 Creighton 103-174 X 2,981,201 4/61 Holdener 103-163FOREIGN PATENTS 554,287 2/23 France. 1,240,080 7/60 France.

321,313 11/29 Great Britain.

764,698 1/57 Great Britain.

827,756 2/ 60 Great Britain.

96,030 9/22 Switzerland.

LAURENCE V. EFNER, Primary Examiner.

ERNEST W. SWIDER UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3 211, 107 October 12, 1965 Vannevar Bush It is herebycertified that error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 14, line 55, for "and" read an column 16, line 50, for"respectivey" read respectively Signed and sealed this 12th day of July1966.,

(SEAL) Attest:

EDWARD J. BRENNER Attcsting Officer Commissioner of Patents

1. A HYDRAULIC PUMP OR MOTOR COMPRISING A HOUSING INCLUDING A POCKETDEFINED IN PART BY OPPOSITELY FACING SURFACES AND AN INTERCONNECTINGSTRAIGHT SUPPORT SURFACE. A FIRST MEMBER RECEIVED IN THE POCKET ANDHAVING A STRAIGHT BEARING SURFACE MATABLY ADJACENT THE SUPPORT SURFACEAND RECIPROCABLE THEREON, A SECOND MEMBER MATABLE WITH THE FIRST MEMBERAND THE OPPOSITE SURFACES OF THE POCKET AND MOVABLE RELATIVE THERETO TODEFINE A VARIABLE VOLUME CHAMBER, SAID SECOND MEMBER HAVING A GENERALLYSMOOTH BEARING SURFACE FACING OPPOSITELY THE FIRST MEMBER BEARINGSURFACE, A SHAFT SUPPORTED FOR ROTATION IN THE HOUSING AND HAVING ASMOOTH SUPPORT SURFACE MATABLY ADJACENT AND MOVABLE RELATIVE TO THESECOND MEMBER BEARING SURFACE AND MOVABLE RELATIVE TO THE SECOND KFROMTHE HOUSING SUPPORT SURFACE FOR MOVING THE MEMBERS RELATIVE TO ONEANOTHER AND TO THE HOUSING, AND INLET AND OUTLET MEANS IN THE OPPOSITESURFACES ASSOCIATED WITH THE CHAMBER, FOR SUPPLYING HYDRAULIC FLUID TOAND FROM THE CHAMBER, EACH OF THE FIRST AND SECOND MEMBER HAV- L ING ATHROUGH PASSAGE OF RESTRICTED CROSS-SECTIONAL AREA EXTENDING BETWEEN ITSBEARING SURFACE AND THE CHAMBER FOR ESTABLISHING A PRESSURIZED FILM OFHYDRAULIC FLUID BETWEEN THE MATABLY ADJACENT SURFACES TO SUPPORT THEMEMBERS ADJACENT BUT SPACED FROM THE RESPECTIVE SUPPORT SURFACES, ANDTHE PRESSURE DROP ACROSS EACH RESTRICTED PASSAGE BEING APPROXIMATELY 1/3TO 1/2 OF THE FLUID PRESSURE ING THE CHAMBER UNDER NORMAL FILM CLEARANCEAND FLOW CONDITIONS.